Hello!
I got one project, now i try to fix all bugs.
My project contains some projects, and start point - Main.project
Almost any classes there is similar error: can not define(gren underlile) imports.

I have a beginner level and understand that solution i must find himself, but i dont know from what start. I saw book VB.NET, but here only basics knowledge and it was not helped.
Must say that all references is active and available.

Are you saying that your Imports statement is underlined in green? In which case you haven't added the correct reference to your project. The NavigationControl error doesn't seem relevent to the first part of your question.
Not sure of the relevence of Error 300 either.
Use the Improve question link to post the code with your first problem - try to fix things one at a time and always start at the top of the list of errors